The invention relates to a scissors lift table comprising a lift platform raisable above and lowerable onto a base frame in a vertical direction by means of a scissors mechanism, the scissors mechanism comprising at least two laterally adjacent scissors arm pairs, each having two scissors arms mutually pivotably coupled in their median region and pivotable relative to each other by a drive device, one end of each of which arms is mounted stationary but rotatably on the lift platform or the base frame and the other end of which is guided slidably in the base frame or the lift platform.
Scissors lift tables of this type are suitable for use wherever loads are required to be raised, for example when charging transfer lines in the motor vehicle body industry, tool packaging machines and processing machines. The drive, at least in the case of lift tables for comparatively heavy loads, is effected hydraulically by one or more hydraulic cylinders mounted on the scissors mechanism, which are loaded during the lifting process with hydraulic fluid delivered by a hydraulic pump driven by an electric motor, a non-return valve bearing provided in the pressure pipe to the hydraulic cylinder(s) in order to prevent any undesired lowering of the lift platform due to a return flow of the hydraulic fluid after the hydraulic pump is switched off. The lowering of the platform is effected by actuating a discharge valve--conveniently incorporated into the non-return valve. However, only relatively slow lifting speeds are achieved with hydraulic lift table drives of this type. Moreover, hydraulic systems are critical as regards the stroke constancy under load, even in the presence of the above-mentioned non-return valve, because leakages may occur in hydraulic systems, which are reflected in (slight) stroke losses. A further difficulty occurs when it is also required to drive the lift platform precisely into one or more intermediate stroke positions in prescribed vertical locations.